1. Field of the Invention
This invention relates to an improved method of producing an acylated derivative of an epoxy fatty acid ester or epoxy natural oil having aliphatic chains of 10 to 24 carbon atoms, and including at least one oxirane segment per molecule, by reacting the epoxy fatty acid ester or epoxy natural oil with a vinyl aliphatic monocarboxylic acid in contact with an acylation catalyst, a polymerization inhibitor and gaseous oxygen, the improvement comprising adding said monocarboxylic acid or said acylation catalyst or a mixture of said monocarboxylic acid and said acylation catalyst to a reaction mixture at an elevated temperature and maintaining an elevated temperature until completion of the reaction.
2. Description of the Prior Art
U.S. Pat. No. 3,125,592 discloses the preparation of polymerizable long chain natural oil and fatty acid ester compounds having vicinal acryloxy and hydroxyl groups. The method disclosed involves mixing an epoxidized derivative of a fatty ester or natural oil, a vinyl aliphatic monocarboxylic acid, a phenolic free radical inhibitor and gaseous oxygen inhibitor with an acylation catalyst at room temperature. The reactants are then heated up to the reaction temperature of 75.degree. to 175.degree. C. and maintained at an elevated temperature until completion of the reaction.
It has been found that the compounds as disclosed in U.S. Pat. No. 3,125,592 are particularly useful as substituents of so-called "100 percent solids" radiation curable coatings and inks, which contain essentially no volatile solvents, are comprised of one or more of the aforesaid compounds, and photoinitiators, and they polymerize upon exposure to radiation to form solid coatings or inks. Such coatings and inks are advantageous to use, since curing them does not require the use of conventional heating equipment, and the associated release of volatile solvents into the atmosphere, yet they can be applied to substrates using conventional liquid film application methods. However, one of the main problems associated with the use of compounds as disclosed in U.S. Pat. No. 3,125,592 is that they typically have high viscosities, which makes them difficult to handle and to formulate with other ingredients in the preparation of inks and coatings. If the viscosity of these compounds could be lowered, this would facilitate variation of the composition of the coatings or inks.